The invention relates to an electrohydraulic control module for making available a compressed fluid, especially compressed oil for actuators that are used for actuating control units, for example, for switching gas-exchange valves of an internal combustion engine on and off, comprising a control housing that is attached to a connection part of the internal combustion engine and that has electric switching valves, which are connected to an oil-supply line and to control lines leading to the actuators.
Such an electrohydraulic control module is described in DE 102 00 4011 638 A1. Deactivating and activating cylinders is used for adapting the piston displacement of the engine to the corresponding power requirements. The lower the required power, the lower the active piston displacement should be. Controlling the engine output by regulating the piston displacement leads to throttling losses and the associated increase in consumption.
In V-engines, the piston displacement is regulated by deactivating and activating the cylinders of one side of the engine. Deactivating the cylinders is performed by locking the closed gas-exchange valves of these cylinders. Hydraulic actuators with pistons that actuate the locking pins are used for this purpose.
Outside of electrohydraulic control modules for deactivating cylinders, those for control systems for transmissions, especially automatic transmissions, are also known. The control module according to the invention also relates to these.
The electrohydraulic control module described in the class-forming publication has a one-piece construction. Its assembly and testing expense is relatively low, but the production expense is relatively high due to the exclusive use of processing involving cutting. This applies primarily for the manufacturing of oil supply lines that extend as bores over the greatest part of the length of the control module.
In U.S. Pat. No. 6,481,409 B1, another electrohydraulic control module is described. This has a multiple-piece construction with a top plate in which the channels are partially machined, with an attached sealing plate that closes the channels, with a closing plate, and with additional holding plates for the switching valves. The plates are sealed from each other and screwed with several screws that also guarantee the attachment of the control module to the crankcase of the internal combustion engine.
This solution is very complicated and expensive because processing of the sealing surfaces is required despite the integrated channels. The large number of parts results in a correspondingly high assembly expense. In addition, the number of seals and the length of the sealing distances put the service life of the seals at risk.
A similarly constructed electrohydraulic control module is described in U.S. Pat. No. 6,439,176 B1. This also involves a multiple-part device that is expensive in production and assembly and that is susceptible to failure.